Reports & briefings.

The statutory floor

In the UK, employers and those in control of non-domestic premises have a duty under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH) to assess and manage the risk of exposure to Legionella from any water system on their premises. The HSE's Approved Code of Practice L8, and its supporting technical guidance HSG274 (Parts 1–3), set out how that duty is typically discharged.

Operationally, this means:

A risk assessment — identifying systems that could give rise to risk (water storage, hot/cold distribution, showers, calorifiers, cooling towers, evaporative condensers), the likelihood of Legionella proliferation, and the people who could be exposed.

A written scheme of control — the actions taken to manage the identified risk: temperature management, flushing of low-use outlets, sampling, cleaning, TMV servicing, and so on.

Monitoring and review — verifying that the controls work, recording what was done and when, and reviewing the assessment regularly and whenever circumstances change.

A named Responsible Person — accountable for managing the risk on the duty holder's behalf, ensuring the scheme is followed and competent contractors are engaged.

What BlueMetric provides

Convenience. Continuous sensor coverage replaces a meaningful share of the manual temperature checks that the scheme of control requires. Readings are taken every 15 minutes, every day, in places where someone would otherwise have to walk in with a probe — sentinel outlets, plant rooms, cold-water storage tanks, TMV groups.

Assurance. When the platform detects a reading outside the thresholds set out in HSG274, it alerts the duty holder, dispatches a certified technician within a defined response time, and seals the entire event — what was measured, when, by whom, what was done — into a tamper-evident record. Weekly compliance certificates are issued without anyone reaching for a clipboard.

Defensibility. Should the duty holder be asked — by an inspector, an insurer, or a court — to demonstrate that the scheme of control was followed, the answer is a continuous record rather than a periodic snapshot. Each reading is SHA-256 hashed, GPS-locked to the deployed site, and chained week to week.

What it doesn't change

The statutory duty stays with the duty holder. The risk assessment still needs to be carried out by a competent person. Some inspections — calorifier internals, mechanical valve testing, structural — still require a competent person on-site. BlueMetric reduces the cadence of the routine checks where defensible; it does not eliminate them.

For most institutional estates, the practical effect is that the everyday compliance loop moves from a paper-based, periodic, reactive workflow to a digital, continuous, auditable one — and the work that genuinely requires a competent person on site becomes the work that competent person actually does.

Why the risk is rising

Three things have changed over the past decade. Building stock has aged. Water-system designs increasingly include longer pipe runs, lower flow rates, and energy-saving controls that can lower hot-water set points. And occupancy patterns — particularly in hospitality, residential, student accommodation and offices — have become more variable, with stretches of low use that allow water to stagnate.

The bacterium itself hasn't changed. The conditions it likes — warm water (20–45 °C), stagnation, biofilm — have become more common in the systems we operate.

What continuous monitoring is solving for

The standard UK approach to Legionella control has been periodic. Temperatures at sentinel outlets are checked monthly. Samples are taken quarterly. The risk assessment is reviewed every two years. In good faith, conscientiously, this is what most institutional estates do.

The structural problem with the periodic approach is the gap between checks. A month is 720 hours. A site visit is 4 to 6. Inside that gap, a cold-water system can drift warm, a hot return can drop below 55 °C, an outlet can stagnate, and the record will simply not show it until the next visit — by which point the conditions may well have resolved themselves, or they may not.

Continuous monitoring is the response to that maths. A reading every 15 minutes for 365 days is over 8,000 data points per sensor per year. Hashed, timestamped, GPS-locked, those readings become a record rather than a sample.

Where governments and industry are heading

The trend across institutional UK facilities management is toward continuous, sensor-based monitoring as a complement to (not a replacement for) periodic site checks. IoT temperature monitoring of water systems is permitted under HSE guidance, and is increasingly written into Legionella risk assessments for buildings where it can be deployed.

Increasingly, procurement specifications and risk reviews — particularly for institutional estates in healthcare, residential and hospitality — include questions about continuous monitoring. The public-health case is straightforward: a continuous record finds problems faster than a periodic one does.

"Compliant on paper, prosecuted anyway"

A subtle but important point: many of the highest-profile UK Legionella and water-safety prosecutions in recent years have not been failures of the periodic regime itself. The duty holders had risk assessments. They had schemes of control. They had contractors.

The failures were in execution — and in the records that purported to evidence it. A risk assessment that didn't match the actual risk profile of the site. A scheme of control whose flushing schedule was on the spreadsheet but not in the field. Temperatures that were "checked" but not in a way the record could later substantiate. Contractor visits that were paid for but not verified. Alerts that were noted but not acted on.

Continuous monitoring directly addresses this category of risk in two ways. First, the act of measurement is automatic: the temperature reading is what the sensor says it is, every 15 minutes, regardless of who happened to be on site. Second, the record of what was measured, when, by whom, and what was done in response is tamper-evident — hashed, timestamped, location-bound — so it can be relied on in retrospect.

A clarifying note. BlueMetric does not eliminate or transfer the duty holder's legal liability under UK health-and-safety law. What continuous monitoring does is improve the evidentiary footing the duty holder stands on if challenged. The statutory duty itself is unchanged.

The institutional move

Care groups, BTR portfolios, hospitality groups and healthcare estates are running continuous-monitoring pilots now. The typical pattern is a single-building pilot, validated over a quarter, then a phased rollout across the portfolio. Pilots are short, intentionally low-cost, and structured so that the operating model is what's being tested — not just the technology.

For duty holders considering this for the first time, the question is rarely "do we replace the existing scheme of control?" — you don't. It's "do we want the next 12 months of compliance evidence on the rising baseline of continuous monitoring, or on the old one?" The maths of the 720-hour window is what's shifted; the rest follows from it.

— BlueMetric Editorial. Draft. Comments via the contact form.